Flexographic printing machines are increasingly used in the printing field. Usually, flexographic printing machines were used to print on bags, wrappers, cartons and boxes. Recently, flexographic printing is being used outside of the packaging field, particularly for books, magazines, stationery and the like A good discussion of flexographic printing is found in "Machine Printing" by Durrant, Meacock and Whitworth, copyright 1973 by Hastings House Publishers, New York, N.Y.
It has previously been proposed to separate inks of different characteristics, for example of different colors with respect to actual zones on an ink ductor roller against which at least one and usually two doctor blades are engaged, see, for exam U.S. application, Ser. No. 921,338, filed Oct. 21, 1986, now U.S. Pat. No. 4,754,701 Batke et al. This application is directed to a system in which a separating plate is located beneath an axially extending doctor blade. The separating plate has a sealing element attached thereto, resiliently engaging the underside of two doctor blades facing the ductor or trough roller from different directions to permit operation of the ductor or trough roller in either direction of rotation. A low friction surface is applied to the edge which faces the doctor blades, the sealing elements spanning the space between the doctor blades and being matched to the circumference of the ductor or trough roller. The doctor blades extend axially beyond the sealing elements. The separating plates and sealing elements can be mounted on units which are actually positioned along on ink trough and hence the ductor or trough roller, at selected positions, as required by the axial extent of different colored inking zones.
German Patent Disclosure Document DE-OS No. 23 20 638, referred to in the aforementioned Batke patent application, describes an arrangement in which two ink separating sheet metal elements are engaged by spring force directly to the circumference of a ductor roller in order to separate differently colored inks from each other. The lateral sealing of the ink reservoir or ink sump region is obtained by engaging the separating elements against the faced surface of the doctor blades or stripper blades.